People in Oklahoma City and its suburbs have felt the rumbling of a series of small earthquakes since Saturday that could be linked to oil and gas production activities.
It began around 4:30 a.m. Saturday with a magnitude 3.7 rupture centered near Edmond and 12 miles northeast of the city. State officials recorded 16 quakes of varying sizes Saturday morning. At 8 p.m. Sunday, a magnitude 3.3 quake hit nearby. Local media say there have not been reports of injuries or damage.
The most recent was a magnitude 3.2 magnitude quake at about 2:30 a.m. today, centered about 14 miles northeast of Oklahoma City, according to preliminary data from the U.S. Geological Survey.
The shaking appears to be part of a well-known seismic pattern called the "Jones Swarm," named after a small town bounded on three sides by the eastern border of Oklahoma City. Seismologists have recorded hundreds of small quakes in the area during the past several years.
Cornell University professor Katie Keranen, who began looking at the Jones swarm while teaching at Oklahoma University, said the quakes appear to be linked to oil and gas activities in the area.
"These most recent earthquakes highlight the continuing seismic activity near Jones and the east Oklahoma City metro area, in a swarm which appears linked to high-volume water production and injection wells in central Oklahoma," Keranen said.
But Austin Holland, research seismologist with the Oklahoma Geological Survey, pointed to natural factors in an interview with an Oklahoma City television station.
"We know why Oklahoma has earthquakes," Holland told KWTV News 9. "It's responding to these large regional stresses that are much smaller than in California, where you can better measure the deformation on a fault."
Keranen presented findings in Denver last month at the annual meeting of the Geological Society of America, drawing some of the first connections between oil and gas production and the Jones swarm.
"Earthquakes began soon after the onset of injection," she wrote in her abstract. "There are commonalities in the methods used for petroleum extraction from carbonate reservoirs in central Oklahoma, involving the production of high water volumes, which speculatively may explain the abundance of induced earthquakes recorded here."
Keranen did the study with three scientists from the Lamont-Doherty Earth Observatory at Columbia University.
Keranen has also linked Oklahoma's largest recorded earthquake, a 5.7 near Prague in 2011, to nearby oil and gas waste injection wells.
Seismologists are also looking at connections between drilling waste injection and quakes in several other areas. Near Marietta in southern Oklahoma, earthquakes started shortly after a new injection well opened in September. State officials have said a series of quakes near Enid, which has some of the state's largest injection wells, might be related to injection.
And Keranen's Jones swarm study also has pointed toward oil and gas activities for a series of quakes in April centered around Luther, Okla. The largest was magnitude 4.3.
State and federal officials warned last week that Oklahoma appears to be in the throes of an earthquake swarm linked to deep underground injection of oil and gas wastewater.
That prompted Oklahoma Insurance Commissioner John Doak to recommended that residents buy earthquake insurance (EnergyWire, Oct. 31).
Scientists say that damaging or even felt earthquakes have not been linked to hydraulic fracturing. Instead they're sometimes caused by the disposal of the immense quantities of wastewater created by fracking and drilling. They can also be produced by removing large amounts of oil or water from underground.